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Spt. 10, 1929. D. N. CROSTHWAIT, JR

VACUUM HEATING SYSTEM Filed June 16, 1928 3 Sheets-Sheet Urn g5.

Se t. 10, 1929. D. N. CROSTHWAIT, JR

VACUUM HEATING SYS TEM Filed June 16, 1928 3 Sheets-Sheet 2 kw QM m M A T ,rlfttOTTlQUS. I

p 1929- D. N. cR sTHwArr, JR 1,727,965

' VACUUM HEATING SYSTEM Filed June 16,1928 5 Sheets-Sheet 3 F" T. 7b 75 7 l-lllsllllllu 6,

v1mm fi qfliorngys Patented Sept. 10, 1929.

UNITED STATES PATENT OFFICE.

DAVID N. CROSTHWAIT, JR., OF MARSHALLTOWN, IOWA, ASSIGNOR TO 0. A. DURHAM COMEANY, OF MARSHALLTOWN, IOWA, A CORPORATION OF IOWA.

VACUUM HEATING SYSTEM.

Application filed June 16,

This invention relates to a Vacuum steam heating system, and more particularly to a system adapted to operate with steam at controlled sub-atmospheric pressures, as disclosed in the patent to Dunham 1,644,11et, granted October 4, 1927.

in a system oi this type, steam is supplied under a vacuum, or at a sub-atmospheric pressure, to an evacuated condensing space or radiator. A reducing valve, or generatorcontrol mechanism, is provided for regulating the sub-atmospheric pressure of the Steam in the radiator. The pressure of the steam determines its temperature, and consequently the amount of heat given out by the radiator. A return main for withdrawi119; air and condensate from the radiator leads through a thermostatically controlled steam trap which prevents the escape of steam from the radiator. An exhausting mechanism operates on the return main to withdraw condensate and maintain the vacuum in the system. A diiierential pres sure controller connected between the supply and return sides of the system governs the operation of the exhausting means so as to maintain a substantially constant and pre- 7 determined diiierence in pressure between the supply and exhaust sides of the radiator no matter what the absolute pressure of the steam in the radiator may be.

in heating buildings in many sections of the country. provision must be made to care for sudden and severe wind conditions. i er example. in certain localities there are times when high winds accompanied by falling temperatures come from the north. In such. instances the north side of a building is hard to heat whereas the other sides may be herded with relative ease. In order to combat this condition, it has been proposed to have separate and distinctheating systemto: the dillerent portions of a building so that steam at a higher pressure and tem perature can be supplied to the heating system in that portion of a building subjected to the more severe weather conditions, while lower pressure steam can be supplied to the system or systems in those portions of the building where less heat required. How- 1928. Serial No. 285,885.

ever, in many instances the cost resulting from the duplication or multiplication of .parts makes this method of procedure prohibitive.

The general object of this invention is to provide a vacuum heating system of this type involving two or more separate and distinct radiating or condensing systems for ditl'erent parts of the building, all of the systems being supplied from the same source of steam, and a single exhausting mechanism being utilized to maintain the requisite sub-atmospheric pressures throughout the various parts of the system.

Numerous other objects and advantages of this system will be apparent from the fol lowing detailed description of certain approved forms of apparatus for carrying out the principles of this invention.

In the acompanying drawings:

Fig. 1 is a diagrammatic elevation showing one form of the apparatus.

Fig. 2 is a view similar to a portion of Fig. 1 showing a modification.

Fig. 3 is a vertical central section through a diil'erential pressure controlled valve.

In Fig. 1 is illustrated an example of a heating apparatus including two seperate radiating systems adapted to operate simultaneously at different sub-atmospheric pressures, although it will be apparent as the description progresses that more than two such systems could be operated in the same manner. Several portions of the apparatus are common to the two heating systems, principal among which are the generator A, the exhausting mechanism indicated genorally at B, the flash tank C, the differential pressure controllers D and E, and numerous auxiliary connections between these several parts as hereinafter described. The generator or boiler A which may be of an approved form, furnishes steam to hea er 1, from which a drip pipe 2 leads back to the lower portion of the boiler at 3. p A normally closed drain connection for the system is indicated at 4.

The exhausting mechanism B is substantially the same as that disclosed in the Dunham patent hereinabove referredto. A centrifugal pump 5 driven by motor 6 withdraws water through pipe 7 from the lower portion of tank 8 and projects this water upwardly through the ejector 9 and thence through pipe 10 back into the upper portion of tank 8. A partial vacuum is created by the liquid. stream within the ejector casing, and the air and condensate withdrawn from the radiating systems through pipe 11 c and one-way valve 12 are entrained within the liquid stream and delivered into tank 8. The air escapes through pipe 13 and outwardly opening check valve 14. Since condensate is continually delivered to tank 8,

"= the water level within this tank will gradua of float 15.

The starting and stopping of motor 6 is controlled by starter 20, connected through leads 21 and 22 with motor 6. The power lines running to starter are indicated at 23Yand 24. Starter 20 is connected by leads 25 and 96 with the switch 27 of the differential-pressure "controller D. This controller may be the same as that disclosed in the Dunham patent above referred to, or in the co-pending application of McMurrin, Serial No. 174,994, filed March 12, 1927. In general, the controller comprises a casing divided into two chambers by a flexible diaphragm. The two chambers are connected respectively with the supply and return sides of one of the heating systemsby pipe connections "hereinafter described. "A'spring tends to urge "the diaphragm in "one direction,'the action of the'spring being balanced by the desired pressure diflerential between 7 separate radiating systems.

the supply "and return sides of the system. lVhen the pressure differential falls below thedesired minimum, the spring will actu- 'ate'the di'aphragm" and a stem projecting therefrom infone direction, thereby closing the switch "27, whichthrough starter 20 starts the operation of motor 6 and exhausting mechanism -B,so "as to'withdraw fluids from the return side ofthefsystem and increase the pressure differential. WVh'en the desired pressureflifferential has been attained, the diaphragn'i. will overcome the spring' and open switch 27 whereupon motor 6 andexhausting mechanism 13 are again temporarily stopped. All of the above is substantially the same as in the Dunham patent hereinabove referred to.

Steam is delivered from the header 1 through sup'ply mains Fand F to the two The principal elements of these systems are substantially identical and comprise a main cut-elf valve G, a reducing valve H, a plurality of radiating units J, a return main K, and other auxiliary elements and connections hereinafter described. The elements of the radiating system at the right hand side of Fig. 1 are indicated by unprimed reference characters, whereas the similar elements of the radiating system at the left of Fig. 1 are indicated by similar primed reference characters. As here shown, the right hand system comprises two radiators J, whereas the left hand system discloses only a single radiator J but it is to be understood that the number of radiators in each system could be increased as found necessary or desirable.

The cut-ofl valve G is normally open when the system is in operation. The reducing valve H may be of a well known form, such as disclosed in the Dunham patent hereinabov referred to. It comprises a pair of balanced valves in the casing 28 for controlling the flow of steam at boiler pressure in the portion 29 of supply main F, into the low pressure portion 30 of this supply main, The valves in casing 28 are controlled through stem 31 from a diaphragm located in casing 32, this diaphragm being subject on one side to atmospheric pressure, and on the other side to the sub-atmospheric pressure existing in the portion 30 of supply main F, this pressure being delivered through supply conduit 33 which connects with supply main F at some little distance -from casing 28 so as not to be influenced by the fluctuations in pressure within the valve chamber. A lever 3 1 fulcrumed at 35 and pivoted at 36 to operating stem 31, supports from its ends the adjustable weights 37 and 38. By properly adjusting these weights, a force is exerted through lever 3a on stem 31 which either assists or opposes the pressure differential exerted on the diaphragm in casing 32. T he resultant force applied to stem 31 either opens or closes the valves in 28. The weights 87 and 38 are so adjusted that when the desired vacuum or sub-atmospheric pressure is attained in the portion 30 of supply main F, the diaphragm in casing 32 will be moved to close the valves in 28 and shut oif the flow of further steam into the supply main from header 1. As the steam in supply main F is condensed or otherwise dissipated, the pressure in the supply main will be lowered whereupon the. diaphragm will be actuated in the opposite direction to open the valves in 28 and admit more steam to the supply main F. This acti on will be substantially continuous so that 1 iii) lit!) steam supplied from generator A through header 1.

This sub-atmospheric pressure steam is delivcred from supply main F to each radiator J through a steam riser 39 and a normally open inlet valve 40. A steam trap 41 is interposed between the lower portion of adiator J and a pipe 42 leading to return main K. lVhen steam from radiator. J enters the steam trap 41 it will expand the operating means within this trap and close the valve to prevent the escape of steam into the return main. lVhcn sufficient condensate or air has accumulated, the valve operating means will be cooled and will contract to open the valve and permit the escape of the condensate and air through pipe 42 to the return main K. The condensate which accumulates in supply main F is delivered through float and thermostatic trap 43, and pipe connections 44 and 45 into return main K. Return main K leads down through cutoff valve 46 to the pipe 11 leading to ejector 9 of the exhausting mechanism B.

An alternative pipe connection 47 branches from return main K above the cut-off valve 46, and leads through a second cut-oft valve 48 into the flash tank C. It will be apparent that when valve 48 is closed and valve 46 open, condensate and air in return main K will be delivered directly to the ejector 9 of exhausting mechanism B. On the other hand, when valve 46 is closed and valve 48 is open, the condensate and air in return main K will be delivered through the alternative pipe connection 47 into the flash tank 0. The flash tank C is provided for the purpose of permitting the condensate returning from the portion of the heating system that is operating at the higher pressure to re-vaporize temporarily as a result of CX panding to the pressure existing in the suction to the vaccum pump. which is substantially equal to the pressure existing in that portion of the system operating at the higher vacuum or lower pressure. The condcnsate accumulating in flash tank C drains through pipe 49, float trap 50 and outlet 51 into one or the other of the return mains K or K, or the pipe 11, and is thence drawn into the exhausting mechanism ll. The purpose of the float trap 50 is to prevent any steam entering the return main as a result of re-evaporation occurring in flash tank C. An equalizing pipe 52 extending from the upper portion of tank C to the float trap 50 permits the ready entrance of condensate into the trap 50.

A pipe 53 leads from the upper portion of flash tank C to a three-way valve L from which branch pipes 54 and 54 lead through steam traps and 55 to the respective return mains K and K. By suitably turning the three-way valve L. the flash tank C is placed in communication through pipe 53 and branch pipe 54 or 54 with the return pipe of that system which is operating at the lower pressure or higher vacuum. The thermostatic traps 55 and 55 are provided to prevent the passage of any steam which might form as a result of re-evaporation 1n flash tank G into the return mains.

The differential pressure controlled valve E (shown in detail in Fig. 3) automatically opens and closes the suction pipe 58. A pair of connected balanced valves 56 close valve openings in the web 57 within valve casing 58 to govern the passage .01: fluid through the valve. The diaphragm yoke 59 is secured by set screw 60 upon an upper extension 61 of valve casing 58. The valve stem 62 extends upwardly from valves 56 through stufling box 63 and is threaded into the lower end of yoke 64 being secured in place by lock nut 65. A lever 66 carrying an adjustable weight 67 extends through yoke 64 and is fulcrumed at one end 68 in the diaphragm yoke 59. A main diaphragm 69 is clamped at its periphery between the two similar annular dished casing members 70 and 71. The lower casing member 70 is secured to the upper flared end 72 of yoke 59 by means of a plurality of bolts 73, a smaller flexible diaphragm 7 4 being clamped between the members 70 and 72. A third diaphragm 75, similar to the small diaphragm 74, is secured against the upper side of casing member 71 by a cover member 76 secured in place by bolts 77. Cover 76 is provided with apertures 7 8 whereby air at atmospheric pressure is admitted to the chamber above the upper diaphragm 75. A pair of diaphragm plates 79, one at either side of the main diaphragm 69, and the spacers 80 and 81 mounted between the diaphragms, are all carried around a stem. 82 which projects through central apertures in the three diaphragnis. T be three diaphragms 74, 69 and 75 are secured together to operate as a unit by the washers 83 and nuts 84 on the respective ends of stem 82, these parts also serve to seal the central apertures in the diaphragms. A stem 85 is threaded into the upper end of yoke 64 and secured in place by lock nut 86, the upper end of stem 85 being secured to the lower end of stem 82 by collar 87. The stops S8 and 89 formed within the casing members 70 and 71 limit the movement of diaphragm 69 in either direction. A pipe 90 is threaded into lower casing member 70 at 91 so as to communicate with the chan'iber between diaphragms 74 and 69 and a pipe 92 threaded into casing member 71 at 93 communicates with the chamber between diaphragms. 69 and 7 5.

The pipes 90 and 92 are adapted to communicate with relatively high and low pressure spaces between which the desired pressure differential is to be maintained. The smaller diaphragms 74 and 75 are each subject on their outer face to atmospheric pressure, so that these diaphragms will constantly balance one another. Their purpose is to avoid the necessity for stufiing bores about the vertically movable valve stem 82. It will be noted that the weight 67 constantly tends to open the valves 56, but this weight is opposed by the higher pressure existing in the chamber beneath diaphragm 69 which tends to lift the diaphragm and hence raise the valves 56 to their closed po sitions. In other words, the pressure differential acting on diaphragm 69 tends to keep the valves 56 closed, and this force is opposed by the weight 67 which tends to open the valve. By properly adjusting the weight 67, when the pressure diitterential falls below the desired minimum the weight 67 will overcome the pressure acting on diaphragm 69 and open the valves. lVhen the pressure differential has again been built up to the desired maximum, this pressure will overcome the weight 67 and lift same so as to close the valves 56.

The pressure control pipes 90 and 92 lead respectively to the two similar'tour-way valves M and N. These valves M and N may be designated respectively the high and low pressure tourway valves, although these terms are merely relative since the pressures of the fluids passing through each valve are normally sub-atmospheric.

An equalizing pipe 94 (in each radiating system) connects the return main K with the supply main F, this pipe including a one-way valve 95 opening toward the supply main F, and a normally open cut-oti' valve 96. The check valve 95 will normally be held closed by the higher pressure in supply main F, but will open if for any reason the pressure in the supply main should fall below the pressure in the return main so as to equalize the pressures in the two pipes. Surge chambers 97 and 98 are conveniently located in the high and low pressure portions of equalizing pipe 94, and pressure control pipes 99 and 100 extend respectively from these surge chambers to the high and low pressure valves M and N. The surge chambers serve to maintain the proper head of water, compensating for the volume displaced by the movements of the diaphragms in the differential pressure control devices. Pressure control pipes 101 and 102 connect the respective high and low pressure sides of diiterential controller D with the high and low pressure tour-way valves M and N.

Assuming first that the apparatus is to be operated so that the radiating system at the right of Fig. 1 (designated by the unprimed reference characters) is operated at the lower pressure or higher vacuum, the fourway valves M and N will be so adjusted that the control pipes 99 and 100 are respectively placed in communication with the pipes 101 and 102 leading to differential pressure controller D, so that the exhausting mechanism B is directly controlled by the pressure differential existing in this lower pressure system. This same adjustment of the valves M and N will place the control pipes 99 and 100 of the other radiatingsystem in communication respectively with the pipes 90 and 92 leading to the difl erential pressure controller E. The three-way valve L will be so adjusted that pipe 53 is in communication with branch pipe 54 leading to the return main K of the lower p essure system. Out-oflf valve 46 will be opened and cut-01f valve 48 closed so that return main K communicates directly with the exhausting mechanism 13. At the same time, cut-oil valve 46 will be closed and cut-off valve 48 opened, so that the other return main K communicates only with the flash tank C.

The lower pressure or higher vacuum system at the right will now operate exactly the same as the usual difierential pressure vacuum system as disclosed in the Dunham patent hereinabove referred to. The subatmospheric pressure of the steam in the radiators J is determined by the adjustment of the reducing valve H, and the exhausting mechanism B will operate inter imttently to maintain the desired vacuum in the system and also to maintan the necessary pressure differential between the supply and return sides of the system. The air and condensate are drawn directly through return main K into the exhausting mechanism B, the air being discharged through vent l3 and the condensate returned at intcrvals to the boiler A through pipe 18.

Tn the other system (designated by the primed reference characters) less vacuum is required since this system is to be operated with steam at a higher pressure since more heat is to be radated. Accordingly, the reducing valve H will be so regulated that supply main F will supply steam to the radiators J at a higher sub-atmospheric pressure. However, it is desirable that a substantially constant pressure differential be maintained between the supply main F and the return main K, as in the radiating system first described. The differential pressure controller E is now responsive to this pressure difierential between the supply main F and return main K. The return main K now discharges into the flash tank C so that the pressure in tank 0 determines the pressure in the return side of this system. The pipe connections 53 and 54 extending to the lower pressure return pipe K affords a means for exhausting the tank C at intervals so as to maintain the desired degree of vacuum in the relatively higher pressure system. When the pressure differential in this system falls below the desired minimum, the pressure controlled valve E will automatically open so that flash tank C is placed in communication through pipes 53 and 54 with the lower pressure return line K, thus lowering the pressure in flash tank 0 and in return main K. When the necessary pressure differential has again been established in this system, valve E will automatically close. The condensate delivered into tank C is drawn out through float trap 50 and delivered through exhausting mechanism B into tank 8. The gases from tank C are exhausted through pipes 53 and 5 1 into return main K and thence drawn out and vented by the exhausting mechanism B.

In an exactly similar manner, when the left-hand radiating system is to beoperated at the lower pressure or higher vacuum, the valves L, M and N are all reversed so that the differential controller D is operated from the left-hand system through control pipe connections 99, 101, and 100, 102. At the same time the differential pressure controlled valve E will be operated by the control pipes 99, 90, and 100, 92. The cut-off valve 46 will be closed and the valve 48 opened so that return main K will discharge into flash tank C. At the same time cut-off valve 48 will be closed and valve 416 opened so that the return line K of the left-hand system will be directly connected with the exhausting mechanism B. The vacuum in tank C is now supplied through suction pipe line 53, 54; running to return line K which now has the higher vacuum.

If it be desired to operate both systems at the same vacuum, then valves 18 and 48 may be closed and valves 46 and -16 opened so that both return lines K and K discharge directly into the exhausting mechanism B. Valves M and N may be so adjusted that either of the radiating systems controls the differential pressure controller D which governs the action of pump motor 6.

A somewhat modified form of the apparatus is disclosed in Fig. 2. In this apparatus, each radiating system is provided with a differential pressure controller D, D, and the control piping is somewhat simplified. Fig. 2 discloses a portion of the apparatus shown in Fig. 1, and it is to be understood that all parts not here shown or not specifically referred to, are the same as already described in connection with Fig. 1. The pressure control pipes 99 and 100 lead from surge chambers 97 and 98 directly to the high and low pressure sides of the differential controller D. In an exactly similar manner, the pressure control pipes 99 and 100 of the other radiating system lead to the respective sides of a second differential controller D. Branch pipes 103 and 103 lead from the pipes 99 and 99 to a relatively high pressure three-way valve R, and in a similar manner branch pipes 104 and 104: lead from pipes 100 and 100 to a relatively low pressure three-way valve S. The valves It and S replace the four-way valves M and N shown in Fig. 1. It will be apparent that each system is constantly connected with its respective differential controller D or D, and that either system may alternatively be connected with the differential controller E by suitably adjusting the three-way valves R and S. The leads 25 and 26 from the starter 20 of motor 6 extend to a double-throw switch 105 from which branch leads 106 and 107 to the switch 27 of controller D, and leads 106 and 107 extending to the switch 27 of controller D. By throwing switch 105 to one side or the other, either controller D or D may be placed in control of motor 6, and the other controller thrown temporarily out of service. Assuming that switch 105 is thrown to the right so that differential pressure controller D governs the motor 6, the valves R and S will be so adjusted that the differentiallycontrolled valve E is connected with the left-hand system through pipe connections 103, 90 and 104, 92. At such a time, the right-hand system will be operating at the higher vacuum and the left-hand system at the higher pressure, as in the system first described. It should be noted that in order to facilitate the disclosure in the diagrammatic views and show all of the piping system, many of the pipes are shown at different elevations from those actually occupied. As a matter of fact, a great many of the pipes are grouped at the same level and would appear one behind the other if so illustrated.

I claim:

1. In steam heating apparatus, a source of steam, two separate radiating systems, means for supplying steam from the source to each of these systems, and means including a single exhausting mechanism for simultaneously maintaining a different subatmospheric pressure in each of these systems.

2. In steam heating apparatus, a source of steam, two separate radiating systems, means for supplying steam from the source to each of these systems, and means for maintaining a different degree of vacuum in each of the systems, including a single exhausting mechanism directly connected with one of the systems, and intermittently effective means interposed between the exhausting means and the other system whereby a lesser degree of vacuum is maintained in the latter system.

3. In steam heating apparatus, a source of steam, two separate radiating systems,

means for supplying steam from the source at reduced pressure to each system, the

"connectinga portion of the lower pressure pressure in one system being maintained lower than the pressure in the other system, a single exhausting mechanism for withdrawing air and condensate from both systems, the exhausting mechanism being in direct connection with the system operating at the lower pressure, a flash tank into which the other system discharges, means for dis chargingcondensate from the flash tanks to the-exhausting mechanism, a suction pipe system with the flash tank, and an intermittently operated valve in this pipe.

4. In steam-heating apparatus, a source of steam, two separate. radiating systems, means for-supplying steam from the source at reduced pressure to each system, the pressure in one system being maintained lower than thepressure in the other system, a single exhausting mechanism for withdrawing air and condensate from both systems, the exhausting mechanism being; in direct connection with the system operating at the lower pressure, a flash tank into which the other system discharges, means for dischargingcondensate from the flash tank to the ex hausting, mechanism, a suction pipe connecting; a portion of the lower pressure system with the flash tank, and a pressure controlled valve in this pipe.

5. In steam heatingapparatus, a source of steam, two separate radiating systems, means lIlCllldlIlg supply mains and return mains for maintaining steam from the source in each of these systems, a. reducingivalve in each supply main whereby the steam is simultaneously maintained at a different subatmospheric pressure in each system, an exhausting mechanism, and connections .be-

tween the exhausting mechanism and the return mains for maintaining a predetermined pressure difi'erential between the supply and return sides of each radiating system.

6. In steam heating apparatus, a source of steam, two separate radiating systems,

tem operating. at the higher sub-atmospheric pressure, a valve in this conduit and: a differentialtcontroller for this valve connected be tween the supply and return sides of the higher pressure system;

, i In steam heating apparatus, a source of steam, two separate radiating systems, means including supply mains and return mains for maintaining steam from the source in each of these systems, a reducing valve in each supply main whereby the steam is simultaneously maintained at a diflerent sub-atmospheric pressure in each system, an exhausting mechanism, a motor for operating the exhausting mechanism, a differential pressure controller for the motor connected between the supply and return sides of the system operating at the lower pressure, a flash tank, the return main of the lower pressure system leading to the exhausting mechanism and the return main of the higher pressure system leading to the flash tank, a pipe connecting the lower pressure return main with the flash tank, a valve in this pipe, and a differential pressure controller forthis valve connected between the supply-and return sides of the higher pressure system.

8-, In steam heating apparatus, a source of steam-, two separate radiating systems, means including supply mains and return mains for maintaining steam from the source in each of these systems, a reducing valve in each supply main whereby the steam is simultaneously maintained at a difl'erent subatmospheric pressure in: each system, an exhausting mechanism, a motor for operating the exhausting mechanism, a differential pressure controller for the motor connected. between the supply and return sides of the system operating at the lower pressure, a flash tank, exhaust pipe connections between the exhausting mechanism and the return main of the lower pressure system and the flash tank, a valve in the exhaust pipe lead ing to theflash tank, the return main of the higher pressure system also leading to the flash tank, and a differential controller for the last mentioned valve connected between the supply and return sides of the higher pressure system.

9. In steam heating apparatus, a source of steam, a heating system comprising a radiator, a supply main, a return main, and a flash tank into which the return main discharges, a second heating system. an exhausting mechanism, means controlling the exhausting mechanism whereby it maintains a lower pressure in the second heating system than the pressure desired in the flash tank, a pipe connection betwen the flash tank and the second heating system, a valve in this pipe, a differential pressure controller for operating the valve, and control pipe connections from the controller to the supply and return-sides of the radiator.

10. In steam heating apparatus, a source of steam, a heating system comprising a radiator, a supply main, a return main, and flash tank into which the return main discharges, an: exhausting mechanism, a second heating system, means controlling the exhausting mechanism whereby it maintains a lower pressure in the second heating system than the pressure desired in the flaslrtank, a pipe connection between the flash tank and the second heating system, a valve in this pipe, a differential pressure controller for operating the valve, control pipe connections from the controller to the supply and return sides of the radiator, and a floatvalve for discharging condensate from the flash tank.

11. In steam heating apparatus, a source of steam, a heating system comprising a radiator, a supply main, a return main, and a flash tank into which the return main discharges, a second heating system, means for maintaining a lower pressure in the second heating system than that desired in the flash tank, a pipe connection between the flash tank and the second heating system, a valve in this pipe, and a differential pressure con troller connected with the supply and return sides of the radiator for operating this valve.

12. In steam heating apparatus, a source of steam, a radiator, a supply main, a return main, a flash tank into which the return main discharges, a second radiating system including a return main, means for maintaining a lower pressure in this second return main than that desired in the flrst return main, a pipe connection between the second return main and the flash tank, a valve in this pipe, and a differential pressure controller connected with the supply and return sides of the radiator for operating the valve.

13. In steam heating apparatus, a source of steam, a heating system comprising a supply main leading from the source, a reducing valve for controlling the pressure in the supply main, a return main, a radiator in open communication with the supply main, connections including a thermostatic trap from the radiator to the return main, and a flash tank into which the return main dis charges, a second heating system, an exhausting mechanism, means controlling the ex hausting mechanism whereby it constantly maintains a lower pressure in the second heating system than that required in the flash tank, a pipe connecting the flash tank with the second heating system, a valve in this pipe, and a differential pressure controller connected with the supply and return mains and operating the valve.

14. In a steam heating system, a generator, a header leading therefrom, two separate radiating systems each including a supply main leaning from the header, a reducing valve in the supply main, a radiator in open communication with the supply main, a return main, discharge connections including a thermostatic trap between the radiator and the return main, and pressure control pipes lead ing from the supply and return sides of the system; an exhausting mechanism adapted to withdraw gases and condensate from the two systems and return the condensate to the generator, a dash tank, valved connections whereby the return mains may be alternatively connected to discharge either into the flash tank or direct into the exhausting mechanism, valved pipe connections leading from the flash tank for alternatively placing same in comnnmication with either return main, a cut-otl' valve in this pipe connection, a ditfcrential pressure controller for operating the valve, a second dill'erential pressure controller for governing the opcrathin oi the exhausting mechanism, and 'alved pipe connections for alternatively placing the prey sure control pipes leading from either radiating system in communication with the respective dili'crential pressure controllers.

15. In a steam heating system, a generator. a header leading therefrom, two separate radiating systems each including a supply .main leading from the header, a reducing valve in the supply main, a radiator in open conununication with the supply main, a return main, discharge connections including a thermostatic trap between the radiator and the return main, and pressure control pipes leading from the supply and return sides of the system: an exhausting mechanism adapted to withdraw gases and condensate from the two systems and return the condensate to the generator. a flash tank, an outlet ior condensate leading from the flash tank to the exhausting mechanism said outlet including a float-trap, valved connections whereby the return main may be alternatively connected to discharge either into the flash tank or direct into the exhausting mechanism, valved pipe connections leading from the flash tank or alternatively placing same in communication with either return main, a cut-otl' valve in this pipe connection, a differential pressure controller for operating the valve, :1 second diflerential pressure controller for governing the operation of the exhausting mechanism, and valved pipe connections tor alternatively placing the pressure control pipes leading from either radiating system in communication with the respective ditlerential pressure controllers.

16. In a steam heating system, a generator, a header leading therefrom, two separate radiating systems each including a supply main leading from the header, a reducing valve in, the supply main, a radiator in open communication with the supply main, a return main, discharge connections including a thermostatic trap between the radiator and the return main, and pressure control pipes leading from the supply and return sides of the system; an exhausting mechanism adapted to withdraw gases and condensate from the two systems and return the condensate to the generator, one of the return mains discharging directly into the exhausting mechanism, a flash tank into which the other return main discharges, a pipe connecting the flash tank with the first return main, a valve in this pipe, a diflen ential pressure controller for operating the valve, a second differential pressure controller for governing the operation of the exhausting mechanism, the pressure control pipes from the system which discharges into the flash tank leading to the first mentioned diflerential controller, and the pressure control pipes from the other system leading to the second controller.

17. In a steam heating system, a generator, a header leading therefrom, two separate radiating systems each including a sup ply main leading from the header a reducing valve in the supply main, a radiator in open communication with the supply main, a return main, discharge connections including a thermostatic trap between the radiator and the return main, and. pressure control pipes leading from the supply and return sides of the system; an exhausting mechanism adapted to withdraw gases and condensate from the two systems and return the condensate to the generator, one of the return mains discharging directly into the exhausting mechanism, a flash tank into which the other return main discharges, an outlet for condensate leading from the flash tank to the exhausting mechanism said outlet including a float-trap, a pipe connecting the flash tank with the first return main, a valve in this pipe, a differential pressure controller for operating the valve, a second differential pressure controller for governing the operation of the exhausting mechanism, the pressure control pipes from the system which discharges into the flash tank leading to the first mentioned differential controller, and the pressure control pipes from the other system leading to the second controller.

18. In a steam heating system, a source of steam, two separate radiating systems, means including supply and return mains for furnishing steam from the source to 1 each of these systems, a reducing valve in extending from the supply and return sides of each radiating system, the two supply pressure pipes extending to one of the valves and the two return pressure pipes extend ing to the other valve, an exhausting mechanism, a motor for operating the exhausting mechanism, a flash tank, the return pipes from the two systems each having alterna tive connections with the exhausting mech anism and the flash tank, valves for controlling these connections, a differential pressure controller for the motor, a pipe connecting the high pressure side of this controller with one of the four-way valves, a pipe connecting the low pressure side of the controller with the other four-Way valve, a three-way valve, pipes leading from this valve to each of the return mains, a pipe leading from the three-way valve to the flash tank, a valve in this latter pipe, a difl erential pressure controller for operating this valve, and pipes leading from the high and low pressure sides of this controller to the remaining ports of the respective four-way valves.

DAVID N. CROSTI-IWAIT, JR. 

